MACON COUNTY LANDFILL #2
(a/k/a MACON COUNTY #2)
DECATUR, MACON COUNTY, ILLINOIS
At the request of the Illinois Environmental Protection Agency (IEPA), the Illinois Department of Public Health (IDPH) conducted a health consultation of the Macon County Landfill (MCL) #2 site near Decatur, Illinois. In December 1983, the site was placed on the Comprehensive Environmental Response, Compensation, and Liability Act Information System (CERCLIS) list . This health consultation evaluates the public health hazards, if any, posed by current site conditions.
The MCL #2 site is an inactive landfill on Hill Road, about 1.25 miles southwest of Decatur, Illinois (Attachment 1). The site is in a rural, agricultural area on approximately 200 acres, but only about 25 acres were used for the MCL #2 landfilling operations. It is bordered by U.S. Highway Route 51 to the east, Hill Road and agricultural land to the north, the Sangamon River about 0.25 miles to the south, and an active landfill to the west. Within 1 mile of the site, approximately 400 people use private wells . Two homes are within 200 feet of the site. Groundwater in the area appears to flow southward toward the Sangamon River.
Including MCL #2, the 200-acre site contains four landfill sections. Macon County Landfills #1, 3 and 4 have been divided into three 25-acre landfill sections. Currently, MCL #4 is the only active landfill . The remaining 100 acres provide a buffer zone between the landfills, the Sangamon River, and area residents (Attachment 2).
In 1977, a permit was issued for MCL #2 to develop and operate as an extension to the original MCL #1 section. It began operations in 1979, but the fill method and the type of liner, if any, are not known. Clay-rich soil excavated from areas south of the landfill was used as cover material. By 1989, a leachate collection and containment system was completed. The collection system consists of large plastic pipes set in a gravel base covered with clay. Leachate collects in these pipes, is occasionally pumped out and disposed of back into the landfill - four of these leachate pipes are on the MCL #2 site. In the early 1980s, MCL #2 was closed and covered with 3 feet of topsoil .
The following wastes may have been disposed of at MCL #2:
- publicly owned treatment wastes
- oily wastes
- polychlorinated biphenyls (PCBs)
- municipal and industrial wastes such as wash inks
- solvent wastes
- waste core sand
- used paint filters
- solid paint waste
- foundry sand
In 1983, approximately 25 monitoring wells were installed around the perimeter of the property. Three of those monitoring wells were installed on MCL #2. Currently, quarterly groundwater monitoring is conducted as part of an on-site monitoring program.
During a Screening Site Inspection (SSI) in 1989 and 1990, Ecology and Environment, Inc. (E & E) collected on-site soil, groundwater, and sediment samples. During a Focused Site Inspection Prioritization (FSIP) in 1995, E & E collected surface water and sediment samples at the confluence an intermittent stream and the Sangamon River. On March 28 and 29, and June 15 and 16, 2000, IEPA collected off-site residential groundwater samples.
In November 2000, construction was started on a vertical barrier or slurry wall. When completed it will extend to a depth of more than 70 feet, and about 1 mile laterally around MCL #1 to the southern intersection of MCL #3 and MCL #4 . The wall is intended to provide a vertical barrier through the shallow water-bearing zone, and thus will reduce or eliminate the potential for contaminant migration away from the landfill, and protect the public from future groundwater contamination. This corrective action will permanently modify groundwater flow across the site.
IDPH staff accompanied IEPA during the June 2000 off-site residential groundwater sampling event. Access to the site was restricted by a gate and fence on the north side, along Hill Road. The site was accessible from the northeastern edge of the property at Hill Road, the location of the former, now-deteriorating office and machine shop. The eastern edge of this area was restricted by a fence along U.S. Highway 51, the Sangamon River and a wooded area to the south. Two homes and a gas-to-energy facility were about 200 feet north of Hill Road on Macon County Landfill Corporation property. The western edge is tree-lined, and a stream and access road are adjacent to MCL #2. The entrance to the access road was through a locked gate.
IDPH compared the results of each environmental sample with the appropriate screening comparison values to select contaminants for further evaluation for carcinogenic and non-carcinogenic health effects (Attachment 3). Chemicals at levels exceeding comparison values or those for which no comparison value exist were selected for further evaluation. The listing of a contaminant of interest does not necessarily mean it will cause adverse health effects if exposure occurs. Table 1 shows the chemicals of interest at the site.
During the 1989 SSI, the on-site surface soil samples showed the presence of polycyclic aromatic hydrocarbons (PAHs), acetone, 2-butanone, antimony and mercury at levels greater than background. No contaminants were found at levels greater than comparison values.
During the 1995 FSIP sampling, surface water and sediment samples were collected along the Sangamon River at its confluence with the intermittent stream that drains into the Sangamon River at the MCL #2 site. Organic and inorganic chemicals were identified at levels greater than background, but not at levels greater than comparison values.
Near the site and within 15 miles downstream of the site no drinking water intakes exist along the Sangamon River. Any site-related contamination entering the river would be diluted before it reached water supply intakes.
During the 1990 SSI, three groundwater monitoring wells were sampled on MCL #2. Volatile organic chemical (VOC) contamination was detected in two of the monitoring samples at levels exceeding drinking water comparison values. The VOCs included 1,2-dichloroethene at 200 parts per billion (ppb), vinyl chloride at 10 ppb, trichloroethene (TCE) at 14 ppb, and toluene at 2,000 ppb . The shallow groundwater flow near the site appears to follow the site topography, which is south toward the Sangamon River.
Groundwater samples collected from monitoring wells in 1999 contained organic and inorganic chemicals. Bis (2-ethylhexyl) phthalate was the only organic chemical identified at levels greater than comparison values. The inorganic compounds exceeding comparison values included arsenic, boron, and manganese. These samples were collected primarily from monitoring wells south and southeast of MCL #2. The shallow monitoring wells were at depths of 10 to 20 feet. Deep monitoring wells were screened at a depth of approximately 45 feet.
In 1999, a leachate well was sampled and compared to concentrations in samples from monitoring wells. Except for barium, the groundwater concentrations were much lower than compounds identified in the leachate. In the leachate well, benzene was detected at 56 ppb and bis (2-ethylhexyl) phthalate was detected at 59 ppb. Also, lead and nickel were detected at elevated levels in the leachate well .
These groundwater and leachate analyses suggest that elevated contaminants from the landfill exist in the downgradient shallow water-bearing zone, around the southern and eastern portions of the landfills.
During the 2000 private well sampling, trihalomethanes were identified in one well at 17 ppb. Further investigation determined this was probably due to hauling water to the well from a chlorinated source. The well was shallow, and in all likelihood produced a low volume of water. It also contained low levels of lead and atrazine. Lead levels appear to be from the water distribution system of the home rather than from the site. The presence of atrazine, a commonly used herbicide, usually suggests that surface water contamination has infiltrated a poorly constructed well.
A second well contained elevated inorganic chemicals, including arsenic at 115 ppb, copper at 1,900 ppb, iron at 150,000 ppb, and lead at 440 ppb [3, 4]. The presence of these chemicals is probably not related to the site; they could be the result infiltration of river silt that contained those metals hauled in 1985 to fill low areas near the well. The black and turbid water samples collected from this well had a sewer-like odor. In December 2000 letters, IDPH advised these residents not to drink their well water. Residents confirmed they are now using bottled water as their drinking water supply.
No other contaminants were identified in any of the other 25 wells at levels greater than comparison values.
Adverse health effects can occur when a contaminant reaches a receptor population through a completed exposure pathway. Partially completed pathways are known as potential exposure pathways. An exposure pathway consists of a source of contamination, environmental media and transport mechanisms, a point of exposure, and a receptor population. Exposure to a contaminant might have occurred in the past, may be occurring now, or could occur in the future. When all the elements linking the contaminant source to an exposed population are present, a completed exposure pathway exists. When one of these elements is missing, only a potential exposure pathway exists.
At the MCL #2 site, no completed pathway exists. A potential exposure pathway exists for shallow contaminated groundwater migrating to the surface in leachate. No private wells are between the landfill and the river where the site groundwater contaminants eventually migrate. Restricted access to the remote site and the small size and low frequency of the leachate suggest that exposures would be infrequent and limited to site workers. Future exposures to chemicals of interest at the site are unlikely, especially when the installation of the vertical barrier wall is completed. This remedial action is designed to reduce the potential for contaminant migration away from the landfill. Although the groundwater at the site is contaminated, no one is exposed to it.
IDPH does not anticipate children will be exposed to contaminants at this site. Though not site-related, elevated levels of arsenic and lead were present in a nearby private well. Children are especially susceptible to impaired neurological development from lead exposure. In a December 2000 letter, IDPH advised these residents not to drink their well water.
The MCL #2 site currently poses no public health hazard. This conclusion is based on current conditions and no redevelopment of the site for residential or commercial use. Site-related contaminants have not been detected in off-site, downgradient residential wells.
The groundwater and drainage from the site appear to flow toward an unnamed tributary of the Sangamon River. The potential for runoff of site-related contamination into the river should be decreased by leachate extraction and the completion of a vertical barrier or slurry wall. The nearest drinking water intakes are more than 15 miles downstream and should not be affected, even if some contamination enters the river.
Access to the site is not completely restricted by fencing, but the wetlands, river, and woodlands provide a barrier from the south, and an active landfilling operation adjacent to the MCL #2 also helps restrict access. Additionally, a final cover has been installed on the inactive landfill portions, including MCL #2. Recent contour work has occurred to establish adequate drainage and vegetation.
A private well in the area has elevated levels of arsenic, copper, iron and lead, but this contamination is not in all likelihood related to the site.
IDPH recommends that -
- IEPA monitor the effectiveness of the vertical barrier once it has been completely installed. This is part of the plan for the site.
- The nearby residents whose well is contaminated should not drink that well water. In a December 2000 letter, IDPH advised these residents not to drink their well water. IDPH has confirmed that the residents are using bottled water for drinking purposes.
If future environmental data suggest remedial action activities are not successful, IDPH will reevaluate the site.
Environmental Health Specialist
Illinois Department of Public Health
- Ecology and Environment, Inc. Focused site inspection prioritization--site evaluation report for Macon County Landfill #2, Macon County. Decatur, Illinois: September 1995.
- STS Consultants Ltd. Assessment monitoring report for Macon County Landfill. Decatur, Illinois: October 1999.
- Illinois Environmental Protection Agency. Residential well sample results for Macon County Landfill. March 2000.
- Illinois Environmental Protection Agency. Residential well sample results for Macon County Landfill. June 2000.
|Chemical||Concentration (µg/l)||Comparison Value|
A = shallow groundwater unit (10-20 feet in depth)
B = intermediate groundwater unit (approximately 45 feet in depth)
µg/l = micrograms per liter
Source: Ref - #2, above.
Comparison Values Used In Screening Contaminants For Further Evaluation
Environmental Media Evaluation Guides (EMEGs) are developed for chemicals based on their toxicity, frequency of occurrence at National Priority List (NPL) sites, and potential for human exposure. They are derived to protect the most sensitive populations and are not action levels, but rather comparison values. They do not consider carcinogenic effects, chemical interactions, multiple route exposure, or other media-specific routes of exposure, and are very conservative concentration values designed to protect sensitive members of the population.
Reference Dose Media Evaluation Guides (RMEGs) are another type of comparison value derived to protect the most sensitive populations. They do not consider carcinogenic effects, chemical interactions, multiple route exposure, or other media-specific routes of exposure, and are very conservative concentration values designed to protect sensitive members of the population.
Cancer Risk Evaluation Guides (CREGs) are estimated contaminant concentrations based on a probability of one excess cancer in a million persons exposed to a chemical over a lifetime. These are also very conservative values designed to protect sensitive members of the population.
Maximum Contaminant Levels (MCLs) have been established by USEPA for public water supplies to reduce the chances of adverse health effects from contaminated drinking water. These standards are well below levels for which health effects have been observed and take into account the financial feasibility of achieving specific contaminant levels. These are enforceable limits that public water supplies must meet.
Lifetime Health Advisories for drinking water (LTHAs) have been established by USEPA for drinking water and are the concentration of a chemical in drinking water that is not expected to cause any adverse non-carcinogenic effects over a lifetime of exposure. These are conservative values that incorporate a margin of safety.
This Macon County Landfill #2 Health Consultation was prepared by the Illinois Department of Public Health under a cooperative agreement with the Agency for Toxic Substances and Disease Registry. It is in accordance with approved methodology and procedures existing at the time the health consultation was begun.
Gail D. Godfrey
Technical Project Officer
SPS, SSAB, DHAC, ATSDR
The Division of Health Assessment and Consultation, ATSDR, has reviewed this health consultation and concurs with its findings.
Lisa C. Hayes
for Chief, SPS, SSAB, DHAC, ATSDR